the net was towed forward by a ship, while wire was paid out and retrieved with a
winch. (c) A 1 m^2 MOCNESS multiple net system ready for lowering. Nine nets can
be released sequentially by a stepping motor that releases restraining cables attached
to bars holding the upper edge of the closing net and the lower edge of the opening
net.
(^) Captured plankton can be examined alive or preserved for various purposes
(chemical analysis, identification, and counting; determination of biomass as
displacement volume or weight; and so forth). Animals for experimentation should be
uninjured, and, for those only readily captured by nets, more healthy specimens can
be caught with fine mesh nets (<100 μm causes less abrasion at the cost of more
clogging with phytoplankton), towing very slowly and using large cod-end containers
with fine mesh ports for gentle draining. Even with all precautions taken, specimens
must be subjectively evaluated for good condition after capture.
(^) In recent decades, it has been popular to distinguish gelatinous zooplankton from
the rest. Many gelatinous forms are delicate, and much new information has come
from gentle collection by divers and submersible- or ROV-borne enclosure devices.
They are species that have very large ratios of water to organic matter; often 98% of
their wet mass is water. This allows them to grow large bodies with minimal
acquisitions of food. Gelatinous composition allows also for rapid population growth,
since large bodies can search or process more water to find food, while not much food
is required to make new bodies. Large bodies are also protected from smaller
predators just because they are hard to ingest. Gelatinous zooplankton now have a
separate group of enthusiasts represented by websites with URLs like David Wrobel’s
“www.jellieszone.com”. Diving techniques have been widely applied by these